Study on the relationship between the mechanical properties and processing for self-reinforced polymers: 1—A theory of stress-induced crystallization for entangled polymer networks

Abstract

A new theory of stress-induced crystallization for entangled polymer networks is presented. It is based on the theory of viscoelasticity with constraints of trapped entanglements and crystallites using a model of fibrillar and lamellar morphology engendered by the extended- and folded-chain crystallization. The probability distribution function of the end-to-end vector for two kinds of constituent chains and the viscoelastic free energy of deformation for two kinds of network have been calculated. The relationships of stress to strain for four types of deformation were derived. The theory is successful in relating the equilibrium degree of crystallinity and the melting temperature to the extension ratio for networks with stress-induced crystallization. Furthermore, the theory provides a theoretical foundation for studying the dependences of tensile modulus and strength on the processing and testing conditions for self-reinformed polymers.